In over my head... already :)

Discussion in '40- & 55-Series Tech' started by fyton2v, Jun 13, 2005.

  1. fyton2v

    fyton2v

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    In over my head... already. Compression suddenly lower?

    So when I first got my rig I did a compression test on all the cylinders of the 2F. All were around 145psi except for #2 which was about 120psi. After much advice gathered from this forum I decided to adjust the valves. So I just completed my first valve job and now I'm confused. For reference I went the service manual route, heated up the engine (it was pretty warm in there) and found TDC. Adjusted 1 2 3 5 7 9 rotated the flywheel 360 and then did the others. Everything seemed to be the correct clearance.

    Now for the sanity check:
    Checked the compression afterwards and it seems like #2 now has about the same compression number as the other cylinders... BUT.... now they are ALL around 120psi. :(

    Just to make sure I didn't make a colossal goof. Valve 1 is exhaust, 2 and 3, intake, 4 and 5 exhaust, 6 and 7 intake, 8 and 9 exhaust, 10 and 11 intake, and 12 exhaust. Please tell me I'm at least correct on that part.

    So, did I screw up the timing or completely blow the valve job? This is my first 40 so I don't know what the engine should sound like when running well. It sounds good to me, but I could easily be missing something horrendous.

    Thanks man.
    Peace
     
    Last edited: Jun 14, 2005
  2. fyton2v

    fyton2v

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    hmmmm

    I may be able to answer my own question. Damn I'm getting good.

    I don't think my engine was warm enough to get accurate numbers on the test. It sat a while after the adjustment. I'll warm 'er up and see if it changes anything.

    g
     
  3. fyton2v

    fyton2v

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    EffinA. Still 120 on a known good cyl and 115 on #2. I guess it was warm enough the first time.

    Input would be much appreciated.
     
  4. muddy12

    muddy12

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    Did you warm up the engine before your first compression test? - if not, maybe some oil leakage past the valve stem seals gave a better seal around the rings, and it may be your first reading that was false? FYI, my 2F with 260,000km has mostly 120psi, with one at 105, but burning quite a bit of oil....
     
  5. Pin_Head

    Pin_Head

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    Don't forget, there are two TDCs for each cam revolution and only one of them is correct.
     
  6. fyton2v

    fyton2v

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    I'm pretty sure the engine was warm on my first test. This one has 130K miles. As far as TDC... In only one of the TDCs was there play in the rocker arm on cyls 1 and 2, so I just assumed that this was the correct starting position.
     
  7. 65swb45

    65swb45 Elder Statesman Supporting Vendor

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    You didn't mention what clearances you were using on the feeler guage?
     
  8. fyton2v

    fyton2v

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    .008 and .014. One thing that I'm not sure about is how easy the gauge should slide under the rocker. I made it pretty tight so a .009 and .015 gauge, respectively, wouldn't fit. Maybe that, combined with some additional closing of the gap after tightening that locking nut could be holding the valves open a bit?
     
  9. Pin_Head

    Pin_Head

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    Probably not a valve adjustment problem, since you got the right TDC and a few thousandths isn't going to matter. It isn't rocket science.

    120-115 isn't bad. The fact that it measured 145 PSI before suggests that your technique or your gauge is not reproducible.

    If it is not burning oil, I wouldn't worry about it.

    BTW, just adjusting the valves is not a "valve job"
     
  10. fyton2v

    fyton2v

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    Pin_Head,

    "valve job"... I see your point. Thanks. Now that you mention it, I think it might be smoking a bit. It's tough for me to tell what it was like before because I really didn't drive it. I should have paid closer attention.

    If it is smoking that would be because I'm burning oil (white smoke) and I can assume that oil is leaking down through the valve opening (valve seat)? This would then mean that the lash is too small? Lash is the gap between the rocker arm and valve stem, right?

    I feel like an idiot talking about this stuff. Anyone want to discuss data communications and internetworking?

    Thanks guys.
     
  11. honk

    honk

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    What's your compression guage like? I mean do you have one that uses a rubber cone that's held into the sparkplug hole, or do you have one that screws in there like a replacement sparker using an o-ring to seal when fully screwed in?

    I've never liked the rubber cone type. They depend too much on the operator's ability to make identical seals in all of the sparkplug holes in an engine and thus make any comparative results almost worthless. The screw in type, if in good condition with clean threads and fine o-ring will give a much more repeatable compression test.

    Though I agree that this isn't one of the world's great mystries you said "Maybe that, combined with some additional closing of the gap after tightening that locking nut could be holding the valves open a bit?" There should not be any variance in the gap between setting and locking it down. If there is then your technique needs improvement. All settings should be verified before considered complete by making sure that there has not been any "additional closing of the gap". If there is, THEN IT HAS TO BE DONE AGAIN.

    Addmittedly it is a learned technique to successfully tighten the locknut without upsetting the gap that involves holding a pressure on the adjusting screw that counters the closing tendency, but if you're going to adjust your own valves you must learn it and not complete the job until you can do it knowing that the gaps are correct and properly secured. Anything less could cost you a cylinder head overhaul at least or an engine overhaul in the worst case.
     
  12. theo

    theo

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    Are you doing the compression test the same way each time? When I do it I pull all the plugs, block the throttle wide open, and crank it until the gauge stops increasing.

    Or getting past the rings.

    You won't cause excessive oil burning by setting the valves too tight. You'll just cause too much overlap between the exhaust and intake stages - trying to breathe fresh air in before all the stale air is blown out. I do it underwater sometimes when I see a really huge wolf eel or octupus.

    10-4!
     
  13. fyton2v

    fyton2v

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    thanks for the info

    it's a screw in tester. Other than the engine being warm I am doing the test differently this time.

    The first time I followed the instructions that came with the tester... but now I've forgotten what they were. This time I just disconnected the LT wire to the distributor, took out one plug, screwed in the tester and cranked it over for about 6 rotations.... give or take. I didn’t push down the accelerator.

    Is this not the correct way?

    Regardless, I'm going to go in there recheck my s*** and make sure I have the lash set correctly. However, I definitely want to have some repeatable compression tests so I can have a bench mark.

    You guys rock.
     
  14. honk

    honk

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    That's the wrong way to do it on two counts (at least).
    All of the sparkers should be removed before any testing so that the engine can turn at it's fastest and most consistent speed during each test AND you need to block open the throttle during all of the tests so that the results aren't skewed by variances in the resistance to the piston's pumping.

    At least six revolutions per cylinder is good.

    Be sure that you're screwing the guage into the hole the same distance and with the same pressure against the seat for all cylinders.
     
  15. theo

    theo

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    You want the throttle plates open so there is no restriction to air flow.

    If you pull all the spark plugs it will turn over faster, but it's OK to do one at a time. I just think it's easier on the battery to pull them all.

    You are right to disconnect the HT (high tension) lead from the distributor. (Forgot to mention it earlier.) I ground that wire while testing because it has real potential to shock you out of your socks!

    good luck, come back with your next results.

    (too slow, oh well)
     
  16. honk

    honk

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    Yours is better, theo, than my pompous-sounding and wordy explanations. It's never too late for clarity :)
     
  17. fyton2v

    fyton2v

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    I did the compression tests again tonight in the correct way. Results were, from 1 to 6, 145-132-132-132-137-145 respectively.

    The first time I tested compression (about 6 months ago) I did it correctly. My memory was jogged by doing it the right way tonight. The previous results were 145-122-145-143-145-144. So it looks like the problem with #2 was improved with a valve adjustment, but I most likely misadjusted the others. I suppose it's not bad for a first try :).

    On another note, I'm pretty sure I was running on 5 cylinders. When I disconnected all the spark plug wires I think one wasn't seated properly. After reconnecting everything my engine is noticeably louder and seems to have more power. Also, for reasons I'm sure I'll understand with a lot more experience, the idle has jumped up what I'd guess to be about 300 - 400 additional RPMs (it was idling nice before). And finally, after I took it for a short drive it didn't want to turn off. It sputtered for a while, seemed to actually start itself, and then conked out all without the help of a key in the ignition. Sounded like Speed Buggy (for those of you who grew up watching cartoons in the 70s).

    Back to the drawing board.
     
  18. honk

    honk

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    Did you maybe forget to remove whatever you used to block open the throttle for compression testing?
     
  19. theo

    theo

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    So now you have compression testing and valve adjustment "under your belt". It's time to learn how to set the timing.

    Pull the cap, rotate the engine so the points are all the way open, and adjust the gap. Then disconnect and plug the vacuum lines to the distributor. Then rotate the distributor with the engine running and a timing light connected until the timing marks line up. You may have to readjust the idle speed as you go since it changes every time you change the timing. (You have to read up on where the marks are and what they mean. I've never tuned a 2F. And I probably forgot a key step.)

    If the timing is advanced too far you can have "run on" like you describe.

    Also, the idle should go up if you add a cylinder! Just adjust it back down to where it goes.

    Try the idle adjustment first and see if the engine shuts off properly. Then go on to timing if you need to. Eventually you will anyway.
     
  20. fyton2v

    fyton2v

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    The gauge I have doesn't realease pressure unless you open a little valve. Once it's screwed in I crank it over using the key and mash down the gas pedal.
     
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